Apparatus for drying pulverant materials

ABSTRACT

APPARATUS FOR DRYING PULVERANT MATERIALS COMPRISING A PLURALITY OF DRYING CHAMBERS ARRANGED VERTICALLY IN MULTIPLE STAGES, MEANS FOR FLUIDIZING AND DRYING A MOISTURE CONTAINING PULVERANT MATERIAL WITH HEAT, WHILE SAID PULVERANT MATERIAL IS CONTINUOUSLY FED FROM THE UPPERMOST DRYING CHAMBER AS IT PASSES THROUGH A FLUIDIZING GAS AND HEAT EXCHANGER MEANS, MEANS FOR ADVANCING SAID MATERIALS THROUGH EACH SUCCESSIVE DRYING CHAMBER, WHILE COUNTERFLOWING HOT GAS AGAINST SAID MATERIALS, SAID MATERIAL COMING INTO CONTACT WITH GAS HAVING PROGRESSIVELY LOWER DEGREES OF HUMIDITY IN THE LOWER CHAMBERS.

Oct. 12, 1971 JIYUICHI NARA 3,511,585

APPARATUS FOR DRYING PULVERANT MATERIALS Filed June 11, 1969 3,611,585 APPARATUS FOR DRYING lliJLVlERANT MATERIALS .Iiyuichi Nara, 2-7-8 Higashi-Ooi, Shinagawa-ku, Tokyo, Japan ll iled June 11, 1969, Ser. No. 832,167 Claims priority, application Japan, June 19, 1968, 43/ 32,362 lint. Cl. F26! 17/00 US. Cl. 34l57 A 2 "Claims ABSTRACT OF THE DISCLOSURE Apparatus for drying pulverant materials comprising a plurality of drying chambers arranged vertically in multiple stages, means for fluidizing and drying a moisture containing pulverant material with heat, while said pulverant material is continuously fed from the uppermost drying chamber as it passes through a fluidizing gas and heat exchanger means, means for advancing said materials through each successive drying chamber, while counterflowing hot gas against said materials, said material coming into contact with gas having progressively lower degrees of humidity in the lower chambers.

SUMMARY OF THE INVENTION This invention relates to a continuous-flow type drying apparatus for pulverant materials which has a plurality of drying chambers arranged vertically in multiple stages.

The present invention has for its object the provision of a drying apparatus for drying organic materials such as synthetic resins and inorganic chemicals wetted or moistened with various organic solvents and water either singly or in mixture, which is able to suspend and fiuidize a large quantity of pulverant material with a relatively limited amount of hot gas, extend the residence time of the particles to a much greater period than in the conventional apparatus using the same amount of hot gas, avoid any wasteful heat exchanging action among the particles, the hot gas for fluidizing the pulverant material, and the heat exchangers, and which can be made relatively compact in construction despite the capability of operating with a high degree of thermal efficiency.

Thus, the invention concerns a multi-stage, continuousflow type apparatus for drying pulverant materials comprising a plurality of drying chambers arranged vertically in multiple stages, the uppermost drying chamber having an air shut-off type inlet port for the supply of pulverant material on one side of the upper portion and an exhaust port for humidified air in the ceiling and also a perforated plate at the bottom and heat exchanger means disposed thereover, a weir plate located on the side of said first drying chamber opposite to the side where there is provided the inlet port for the supply of pulverant material, said weir plate defining a discharge port for the pulverant material which overflows and a discharge port for the underfiowing material, the drying chamber in the stage immediately below said first chamber utilizing the discharge ports of the first chamber as the ports for the supply of pulverant material and using the perforated plate for the first chamber as the ceiling and also being provided with another perforated plate at the bottom which carries heat exchanger means thereover, said lower drying chamber being further provided with a weir plate and two discharge ports for pulverant material on the side opposite to the side where there are provided the two inlet ports for said chamber, and still another drying chamber of the same construction as said second chamber being disposed thereunder in multiple stages, the lowermost drying chamber unlike the upper chambers having a hot gas communi- 3&1 l,5@5 Patented Oct. 12, T971 cating chamber and a duct for the introduction of hot gas blast under the perforated plate, and a cyclone collector in communication with the gas exhaust port of the uppermost drying chamber, said cyclone collector being provided with a powder discharge pipe which is open in a desired drying chamber and also with a gas exhaust pipe in communication with said hot gas communicating chamber of the lowermost drying chamber through known means for conditioning the hot gas such as for cooling, drying, heating and compressing said gas.

For a better understanding of the present invention, description will now be made with reference to the accompanying drawing showing an embodiment thereof.

BRIEF DESCRIPTION OF THE DRAWING The single figure in the drawing is a schematic side view, in vertical section, of an exemplary form of multistage, continuous-fiow type apparatus for drying pulverant materials in accordance with the present invention.

DETAIL OF THE INVENTION To realize the object above set forth, this invention provides an apparatus as shown, in which a plurality of drying chambers, generally indicated at I, II and III, are arranged vertically in multiple stages. The uppermost drying chamber I has an air shout-off type inlet port 1 for the supply of pulverant material on one side of the upper portion and an exhaust port 2 for humidified air in the ceiling. The chamber also has a perforated plate 3 at the bottom and heat exchanger means 4 disposed thereover. Said heat exchanger means are such conventional system as flow a heat medium through a pipe line. A weir plate 5 is located on the side of the first drying chamber I opposite to 'the side where there is provided the inlet port 1 for the supply of pulverant material. This weir plate defines a discharge port 6 for the pulverant material which overflows and a discharge port 7 for pulverant material which overflows and a discharge port 7 the underflowing material. The drying chamber II in the stage immediately below said first chamber utilizes the discharge ports 6 and 7 of the overlying chamber I as the ports for the supply of pulverant material and uses the perforated plate 3 for the drying chamber I as the ceiling. At the bottom of the lower chamber II there is provided a perforated plate 3 which carries heat exchanger means 4 thereover. The lower drying chamber II is provided with a weir plate 5 and two discharge ports 6 and 7 for pulverant material on the side opposite to the side where there are provided the two inlet ports 6 and 7. In the same way still another drying chamber of the construction identical with the chamber II is disposed thereunder in multiple stages. Unlike the drying chamber II, the lowermost chamber III has a hot gas communicating chamber 8 and a duct 9 for the introduction of hot gas blast under the perforated plate 3". The gas exhaust port 2 of the uppermost drying chamber I communicates to a cyclone collector 10, which is provided with a powder discharge pipe 11 which is open in a desired drying chamber and is also provided with a gas exhaust pipe 12 in communication with the hot gas communicating chamber 8 of the lowermost drying chamber through known means 13 said means 13 is one of conventional type for conditioning the hot gas such as for cooling, drying, heating and compressing the same for example Pebody scrubber."

In the figure, reference numeral 14 designates a conventional rotary valve provided on the line for the introduction of the pulverant material from the cylone collector 10 into the drying chamber 1, II or III, and the numeral 15 designates a change-over valve for selecting the drying chamber through which the pulverant material is to be recycled. Said ports 1, 6, 7, 6', 7, 6", 7" are provided with a conventional air shut-oil valve respectively, for example rotary valve.

Description will be made hereunder on how the apparatus according to the present invention is operated.

To begin with, damp pulverant material is fed into the drying chamber I through the inlet port 1, While steam or hot water is circulated through the heat exchanger means 4, 4' and 4" and hot gas is forced into the hot gas communicating chamber 8 through the line 9.

The damp pulverant material is fluidized over the perforated plate 3, heated and dried by subjection to heat from the heat exchanger means 4, and is led through the spaces above and under the weir plate and thence through the discharge ports 6 and 7, into the underlying drying chamber II. Inside the lower drying chamber II the pulverant material is fluidized over the perforated plate 3', heated and dried through contact with the heat exchanger means 4', and is discharged from above and below the weir plate 5 to the discharge ports 6' and 7 The pulverant material supplied from the discharge ports 6' and 7' into the another underlying drying chamber is subjected to a more intense heating and drying action than in the drying chamber II and is led to the ensuing drying chamber or chambers. In the lowermost drying chamber III it is dried to a desired extent and is finally delivered out of the apparatus via the discharge ports 6 and 7 Discharge ports 7, 7' and 7" are necessary because coarse powders are mixed with the fine powders, and some particles fuse together, and these coarse powders do not readily flow over the tops of the weir plates. In the absence of the lower outlets at 7, 7 and 7, the larger particles would accumulate in the drying chamber.

From the air discharge port '2 on top of the uppermost drying chamber I, the gas containing the pulverant material is sent to the cyclone collector 10. The exhaust gas is delivered to the known means 13, be controlled humidity by cooling subsequently be heated and compressed, will be delivered to the hot gas communicating chamber 8 of the lowermost drying chamber III. At the same time, the pulverant material collected by the collector 10 is recycled through the rotary valve 14 and the change-over valve 15 into a desired drying chamber.

The operation of the apparatus according to the present invention, as above described, will be better understood from the following example in which a polypropylene polymer moistened with heptane as a solvent is dried.

The polypropylene resin in powdery form is fed through a centrifugal dehumidifier to the drying process as moistened to 3O 45% W.B. (water base) with heptane. The pulverant material in this state is readily dried by a gas at a relatively high temperature (with a dew point of 45 60 C.) to the primary equilibrium moisture content of 1.5-2.0% W.B. In order to obtain a dried product with an ultimate desired moisture content of 0.1% W.B., the temperature of the material itself must be increased to about 120 C. while the material is in thorough contact with a 'gas at low temperature (with a dew point of 15 to C.).

Generally, however, the use of a low-temperature, lowdew-point gas involves much initial investment and high operation cost. This cost tendency becomes intense in proportion to the volume of gas to be handled.

The present invention is based on the finding that the drying after arrival at the primary equilibrium moisture content is accomplished chiefly by the contact of the pulverant material with a low humidity gas and by the rise of the temperature of the material itself, and it thus provides the apparatus in which the amount of gas to be used is greatly economized by the provision of multiple stages for the fluidization of the pulverant material wherein heat exchanger means are installed and hot gas is supplied.

Thus, the polymer with a primary equilibrium moisture content which is continuously fed from the uppermost drying chamber I is fluidized and, at the same time, dried with heat as it passes through the fluidizing gas and heatexchanger means 4,4 and 4''. The polymer advances through the drying chambers I, II and III wherein the passages for the material are provided counter to those for the hot gas, and comes into contact with gas with lower degrees of humidity in the lower chambers. After a predetermined period of residence, the polymer dried to a desired degree is discharged out of the system. In addition, the temperatures of the heat exchanger means 4, 4' and 4" are progresssively increased in the upper stages so that the pulverant material can be dried up smoothly.

With the construction and performance as above described, the pulverant material drying apparatus according to the present invention can most effectively use up the heat amount of the material particles, hot gas, and heat exchanger means. Among other advantages of the invention are the use of a remarkably reduced amount of hot gas and the consequent compactness of the construction.

I claim:

1. An apparatus for drying pulverant materials having about 30 to 45% water base having means for downwardly feeding the moisture-containing pulverant materials through successive vertical treating zones while upwardly counterflowing a hot gas having successively lower degrees of humidity, said means comprising in combination:

(a) an elongated vertical column;

(b) a plurality of drying chambers arranged vertically one under the other in multiple stages in said column;

(c) an air shut-off type inlet port in the uppermost drying chamber for supplying pulverant material on one side of the upper portion of said uppermost drying chamber;

(d) an exhaust port for humidified air in the ceiling of said uppermost drying chamber;

(e) a perforated plate at the bottom and heat exchanger means disposed thereover in said uppermost drying chamber;

(f) an elongated vertical weir plate located on the side of said uppermost drying chamber opposite to the side Where there is provided said inlet port extending upwards into the chamber, said weir plate defining a first discharge port exhaust way with a rotary valve therein for the pulverant material which overflows said plate and a second discharge port exhaust way for the material underflowing said plate also with a rotary valve therein, the drying chamber in the stage immediately below said uppermost drying chamber utilizing the discharge ports of the first chamber as the ports for the supply of pulverant material and using the perforated plate for the first chamber as the ceiling;

(g) a second chamber, a perforated plate in the second chamber at the bottom and heat exchanger means thereover, said second drying chamber being further provided with a weir plate similar to that of said uppermost drying chamber and two discharge port exhaust ways with rotary valves therein for pulverant material on the side opposite to the side where there are provided the two inlet ports for said chamber so that the ports of supply and discharge of the pulverant material in said second chamber are opposite to those in said uppermost chamber;

(h) at least a third drying chamber with a weir plate, two discharge port exhaust ways with rotary valves therein serving as the lowermost drying chamber of the same construction as said second chamber disposed vertically thereunder, said lowermost drying chamber including a hot gas communicating chamber, a perforated plate with a duct for the introduction of hot gas blast under said perforated plate;

(i) a cyclone collector and a communication line in communication with the gas exhaust port of the uppermost drying chamber, and also with a gas exhaust pipe in communication with said hot gas communicating chamber of the lowermost drying chamber including means for conditioning the hot gas such as for cooling, drying, heating and compressing said gas; and,

(j) passages defined in each of said chambers for the flow of pulverant material therethrough counter to the passage of hot gases, whereby said pulverant material advancing through each successive lower chamber comes into contact with gas having progressively lower degrees of humidity.

2. An apparatus for drying pulverant materials as recited in claim 1 wherein said cyclone collector is provided with a powder discharge pipe which is open in a drying chamber other than said uppermost drying chamber.

References Cited UNITED STATES PATENTS FREDERICK L. MATTESON, Primary Examiner H. B. RAMEY, Assistant Examiner 

